The structure and function of several proteins or groups of proteins will be examined and the structural basis for their specific biological activity will be determined. Five different kinds of proteins will be studied: 1) lactose synthetase, which is composed of two protein components, alpha-lactalbumin and a galactosyl transferase, will be characterized in detail in order to assess how the two proteins interact to support and regulate lactose synthesis. 2) Glycosyl transferases, which are involved in the biosynthesis of oligosaccharide side chains of glycoproteins, will be isolated and characterized by highly specific methods of affinity chromatography employing agarose derivatives of appropriate nucleotides and saccharides. 3) Superoxide dismutases, which contain different metal prosthetic groups, will be submitted to sequence analysis. This includes the copper-zinc form of bovine erythrocytes, the manganese form from E. coli and mitochondria as well as the iron-containing form from E. coli. 4) Crotonase (enoyl-CoA hydratase) from liver will be submitted to sequence analysis and its structure examined in view of its enzymic properties. 5) Human fibrinogen and fibrin will be examined in order to gain further insight into their structures, including the nature of crosslinking by Factor XIII and the nature of the fragments produced on plasminolysis of the two proteins. It is hoped that these studies will provide information of specific as well as general interest.